Flexible duct can be used in heating, ventilation and air conditioning systems to convey warmed or cooled air. For purposes of maximizing energy efficiency, the flexible duct can be insulated. Accordingly, flexible insulation (also called flexible duct media) can be used to insulate the flexible duct.
Flexible duct often includes at least one layer of fibrous insulation. The thickness and density of the layer of fibrous insulation are factors in determining the insulative value (R value) of the flexible duct. Layers of fibrous insulation that are thicker provide more insulative value than layers of fibrous insulation that are thinner.
Conventional flexible duct can be manufactured using blankets of fibrous insulation having different thicknesses and densities. It would be advantageous to provide a more efficient method of manufacturing flexible duct. Additionally, in current practice, flexible ducts are manufactured with three different insulative values, each for a wide range of duct diameters. This requires the manufacture, storage, and handling of a great number of different flexible duct media products by both the flexible duct media manufacturers and the flexible duct manufacturers. If the number of different flexible duct media products could be reduced while yet allowing the manufacture of flexible ducts with the current range of insulative value and duct size, this would increase the efficiency with flexible ducts are manufactured and also lead to an overall lowered manufacturing cost. One of the purposes of the present invention to provide just such efficiency and cost improvement.